There are an estimated 600,000 children under six years old with elevated blood lead levels with 5,000 per year undergoing treatment. In adult medicine, increased total body burden of lead has been associated with the development of kidney disease, hypertension, gout, and neurologic disease. The estimated population effected is in the tens of thousands. Yet, there is no generally available technique to measure total body lead burden. This proposal describes development of a technique using X-ray fluorescence in a transmission geometry to measure total lead, in vivo, non-invasively. Experiments will investigate the distribution of lead bone stores in cadavers. Results will be used to design and build a prototype lead measurement machine for adults. Pilot studies will validate the technique clinically. (Laboratory feasibility has previously been demonstrated.) Design of a pediatric machine will also be undertaken. The ultimate machines will be useful as (1) a diagnostic tool in determining the presence of lead poisoning and elevated levels of body lead; (2) as a monitoring device in following the progress of chelation treatment; and (3) as a screening device to complement or replace erythrocyte protoporphyrin testing in children and to do epidemiologic studies in adults and children.